Headache without red flags (migraine, tension-type, chronic stable)

ACR AC Headache (2022 rev)

A stable primary headache disorder with a normal neurological examination has a yield from imaging close to the background rate of incidental findings, so the scan is at least as likely to create a new problem as to solve the presenting one.

Headache meeting the pattern of migraine, tension-type or chronic daily headache, unchanged in character, with a normal neurological examination and no red flag feature.

Referenced decision support — confirm against your local protocol.

Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.

The request in front of you

Everything is optional. Leave a field alone and the answer assumes nothing — the verdict updates as you go.

Study requested

What the referrer actually asked for. It is evidence of intent, not a constraint on the right answer.

Contrast as written

What the request form says, not what it should say.

Age

Pick a band, or type an exact age if it matters.

years

Pregnancy status

Time since onset

Decides thrombolysis and thrombectomy windows, testicular salvage, and whether an ischaemic limb is still salvageable.

Focal neurological deficit

Immunosuppressed

Changes the differential rather than the modality.

Red flags

These accumulate rather than exclude. Back pain with one of these is a different question from back pain.

Renal risk factors

The question a vetter can actually answer from the request. An explicit “none known” is a real answer, and it removes checks rather than deferring them.

Previous contrast reaction

The pathway — tap anything already done

Marking a study complete moves the answer on. A patient arrives partway through a pathway far more often than at the start of one.

Imaging may not be indicated

MRI Brain — routine unenhanced

MRI Brain

What we'd amend, and why

In a patient whose headache fits an established primary headache pattern and whose neurological examination is normal, the rate of findings that change management is very low, while the rate of incidental findings — arachnoid cysts, small meningiomas, non-specific white matter change, unruptured aneurysms — is not. Each of those generates follow-up, further imaging, insurance and driving consequences and durable anxiety. Imaging may not be indicated here, and saying so is the useful clinical act.

Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.

How was this decided?

pathwayadult — Adults with a stable primary headache disorder
rulerule-mr-device-screening — MR safety screening for implants and foreign bodies; checked by Radiographer at the scanner
rulerule-paeds-sedation — Sedation or anaesthesia for a child; checked by Nurse before the scan

Decision support only. Local protocol takes precedence.

Handled at the scanner(1)nothing for you to do

Settled and owned downstream. Each returns to a radiologist only on the stated trigger.

MR safety screening for implants and foreign bodies
Complete the MR safety questionnaire, verify implant labelling and its stated conditions of use against this scanner and this protocol, and ensure no ferromagnetic object enters Zone IV.
Radiographer at the scannerBefore the scan
Flags back if: An implant or retained foreign body that is MR Unsafe, unlabelled, or cannot be identified; or an MR Conditional device whose stated conditions this scanner or the requested protocol cannot satisfy; or a credible unexcluded intraocular metallic foreign body history.

Worth asking the referrer (1)

None of these hold the request up. They sharpen the protocol or the plan that follows.

Is there any red flag feature: new or changed pattern, age over 50 at onset, papilloedema, focal signs, malignancy, immunocompromise, positional character, pregnancy or preceding trauma?
A single red flag moves the patient onto a different card with a different answer. Its absence is what makes this card apply.

Pathways

Big forks are separate pathways; the first whose conditions match is the one used.

Headache measured in hours — this is not a chronic stable headache

Role	Study & protocol	Why this answers the question
First line	CT Head CT Head — Unenhanced usually appropriate	A headache that started a few hours ago cannot be a stable primary headache disorder, whatever the request form says, so this card's default answer does not apply to it. The immediate question is haemorrhage, and unenhanced CT answers it now; if the onset was thunderclap the subarachnoid haemorrhage pathway governs, and the hours between ictus and scan decide what a negative study is worth. Where the history really is years of migraine with an ordinary attack today, the pattern has not changed and the conversation returns to the one below.
Second line	MRI Brain MRI Brain — routine unenhanced	What follows a normal CT if the headache remains unexplained and the pattern is genuinely new: it covers the posterior fossa, the pituitary, the venous sinuses and the signs of intracranial hypotension that CT does not.

Malignancy, immunocompromise or suspected infection — the wrong card, and contrast is needed

Role	Study & protocol	Why this answers the question
First line	MRI Brain MRI Brain — with gadolinium usually appropriate	The absence of red flags is what makes this card apply, and one has been supplied — so the answer this card otherwise gives is withdrawn rather than qualified. Metastatic and leptomeningeal disease, abscess and the opportunistic infections of immunosuppression are all defined by enhancement, which makes the enhanced study the first one rather than a later refinement. Move to the red-flag headache pathway.

This arm exists to refuse the card, not to endorse imaging in general. The red flag is the indication, and naming it on the request is what justifies the study.

Focal deficit, progressive deficit, weight loss or night pain — the wrong card

Role	Study & protocol	Why this answers the question
First line	MRI Brain MRI Brain — routine unenhanced usually appropriate	A focal sign, a progressing deficit, unexplained weight loss or headache that wakes the patient are the features that move a headache off this card altogether. MRI is the study because it covers the parts of the differential that CT resolves poorly — posterior fossa and pituitary lesions, early tumour, venous sinus thrombosis, intracranial hypotension — and this group will often be imaged again, which is a further argument against ionising radiation. Contrast is added when the suspicion becomes neoplastic, infective or meningeal.

Adults with a stable primary headache disorder

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	MRI Brain MRI Brain — routine unenhanced usually not appropriate	In a patient whose headache fits an established primary headache pattern and whose neurological examination is normal, the rate of findings that change management is very low, while the rate of incidental findings — arachnoid cysts, small meningiomas, non-specific white matter change, unruptured aneurysms — is not. Each of those generates follow-up, further imaging, insurance and driving consequences and durable anxiety. Imaging may not be indicated here, and saying so is the useful clinical act.
Reasonable alternative	CT Head CT Head — Unenhanced usually not appropriate	Substituting CT does not rescue the request. It adds ionising radiation to a study with the same very low yield, and it answers less of the differential than the MRI it replaced. If imaging is genuinely not indicated, the response is not to choose a cheaper scan.

Where a clinician has weighed all of this and still wants the study, that is a legitimate decision for the treating team. This card supports the conversation rather than replacing it.

Pitfalls

Reading "usually not appropriate" as "never". A patient whose headache pattern has genuinely changed belongs on the red flag pathway, and the history on the request form is often thinner than the history in the room.
Assuming that a negative scan will end the consultations. It reliably does not, and the incidental findings it generates create new ones.
Missing a red flag hidden in a long history — a new positional element, a subtle field defect, recent immunosuppression.
Declining without offering the alternative. The useful output is a suggested clinical route, not simply a refusal.
Applying this card to a new or changed headache in a patient over 50. That is the red-flag pathway, and the diagnosis this card must never answer with "imaging may not be indicated" is giant cell arteritis — inflammatory markers and corticosteroid on suspicion, confirmed by temporal artery ultrasound or biopsy, with irreversible visual loss as the price of the delay.

What makes a good request

This is not a refusal to help. It is a statement that the probability of a clinically meaningful finding is very low and the probability of an incidental one is not, and that the right next step is usually a clinical one.
Anxiety and a request for reassurance are legitimate clinical problems, but imaging reassures poorly and briefly, and an incidental finding converts a well patient into a followed-up one.
If the history has actually changed — new pattern, new severity, new neurology, new age of onset — this is the wrong card and the red flag pathway applies instead.

How these studies are acquired

Contrast, phases and timing for every study on the pathways above.

CT Head — Unenhanced MRI Brain — routine unenhanced MRI Brain — with gadolinium

Confirm locally

MRI Brain — routine unenhanced: timings are typical — confirm against local protocol.
Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.

References

Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.